Although electric power has many benefits for use in industrial material transport machinery, some of these benefits may be offset by the need to carry, charge and maintain a sufficient source of electric power, e.g., a large battery or other charge storage system. In applications having substantially repeated travel patterns, such as in mine work and other similar contexts, trolley line systems eliminate this problem by providing a path along which a travelling machine may receive electric power from one or more power lines (herein referred to as “trolley lines”). Such trolley lines may be placed continuously along a path, or only at certain portions of the path, such as uphill runs, to provide assist power.
In a trolley system, the source of electrical power, which may be a municipal grid or an on-site generator facility, stays fixed, but the trolley-powered machine nonetheless receives power from the power source anywhere along the trolley lines. As such, the efficiencies of electric power may be obtained when needed without the concomitant complications and expense of large batteries. However, one significant limitation of trolley systems is that the trolley-powered machine must track the trolley lines if it is to receive power there from. In a related vein, the apparatus for electrically connecting the trolley-powered machine to the trolley lines, called a “pantograph,” must be raised when the trolley line is to be used, and lowered at other times.
Taking into account the above requirements, the use of a trolley system requires the machine operator to both follow the trolley line accurately and to raise and lower the pantograph at the appropriate locations. Failure to meet either requirement can result in a loss of efficiency, since alternative power such as an onboard engine must be used when the trolley-powered machine is not receiving power from the trolley line. Moreover, misdirection of the machine or the pantograph can result in damage to the machine as well as to the trolley line and associated infrastructure, e.g., lines, line poles, transformers, etc.
Although flags may be used to signal the operator regarding locations for raising and lowering the pantograph, and pieces of tape may be applied to the machine windshield to assist the user in “aiming” the machine along the trolley lines, these techniques are not ideal. For example, the use of external visual cues such as these require ample external lighting along the trolley line, including the periphery of the roadway where flags may be placed. Moreover, in certain conditions such as heavy fog or windblown sand, it may be difficult for the operator to clearly see the external visual cues regardless of lighting (e.g., to see the flag beside the roadway or to see the trolley line from between the aiming tapes).
The reference DE10256705 appears to describe a system that detects the electrical conductors of a trolley line by sensing a current in the lines via non-contact means and then steers the truck in response, while potentially displaying the line position to the operator. However, the detection of the lines in such a manner has not particularly effective, and moreover, a user-friendly and effective display system has not taught. Thus, an improved system for operator guidance in a trolley line system is needed.
It will be appreciated that this background section was created by the inventors for the reader's convenience. It is meant to discuss problems and concepts noted by the inventors, and not to discuss or explain prior art unless expressly otherwise noted. Thus the inclusion of any problem or solution in this section is not an indication that the problem or solution is prior art.